Steam generating furnace



1 Aug. 25, 1942. J. H. ROHRER STEAM GENERATING FURNACE Filed April 14, 1959 2 Sheets-Sheet 1 1N VENTOR. Jsz'aizIBo/zn 5 Tu.) WE

' ATTORNEY.

Aug. 25, 1942. RQHRER 2,294,242

' STEAM GENERATING FURNACE Filed April 14, 1939 2 Sheets-Sheet 2 INVENTOR:

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BY 57m 2 ATTORNEY.

Patented Aug. 25, 1942 UNITED STATES PATENT oFFicE STEAM GENERATING FURNACE Josiah H. Rohrer, Philadelphia, Pa.

Application April 14, 1939, Serial No. 267,797

2 Claims.

The present invention relates to furnaces for steam generation and more particularly to a steam generating furnace which is adapted for the burning of bark and similar bulky waste materials.

In many instances, in the combustion of waste materials, it has heretofore been necessary prior to introducing the material into a furnace for combustion to pass the material through a drier or the like, to reduce the moisture content thereof. The furnaces heretofore available for burning Waste materials such as bark, wood-wastes and the like, have generally been of the Dutch oven type, with the fuel usually fed through the roof of the furnace. A large fire space and large grate area are required with such a furnace and suitable bridge walls and arches have been thought necessary in order to obtain proper combustion. With such furnaces also, it has not heretofore been possible to burn the waste material in the most effective manner so that the heat of the combustion could be utilized for steam generation.

In accordance with the present invention the bark, wood-wastes or the like, after shredding or reduction in size so that the fuel material may be handled, may be burned without the necessity for the preliminary drying which was heretofore thought to be necessary. At the same time, the steam generating structure employed with the furnace is of a type which permits of proper utilization for steam generation of the heat released by the combustion.

It is an object of the present invention to provide a furnace construction for steam generators which is particularly suitable for the burning of bark, wood-wastes and similar bulky materials.

It is a further object of the present invention to provide a steam generating unit which will be capable of utilizing relatively wet bark, woodwastes and the like, and in which a drying action with the accompanying drawings forming part hereof, in which:

Figure 1 is a vertical view of a furnace, embodying the main features of the present invention, the furnace being shown partly in vertical section and partly in fragmentary elevation;

Fig. 2 is a front elevational view of the furnace shown in Fig. 1, parts being broken away to show the interior construction thereof;

Fig. 3 is a horizontal sectional View taken approximately on the line 3-3 of Fig. 2;

Fig. 4 is a fragmentary elevational View of one of the upper air ducts; and

Fig. 5 is a fragmentary elevational view of one of the lower air ducts.

Referring more particularly to the drawings in which a preferred embodiment of the invention is illustrated, it will be seen that the furnace and steam generating unit includes a front wall I0, a rear wall II, side walls I2, a top wall I3, and a bottom wall or floor I4. An upper steam drum I5 is preferably mounted in the upper rear part of the furnace. An upper front header I6 is preferably mounted at the junction of the front wall III and the top wall I3. A middle front header I! is preferably mounted at a medial location in the front wall I 0 and a rear header I8 is preferably mounted at a medial location in the rear wall I I. The side walls I2 also preferably have near the bottom thereof a lower header 20 and at the upper portion thereof an upper header 2|.

Banks of tubes 22 are provided for connecting the upper front header It with the steam drum I5 and. the uppermost group of tubes of the bank of tubes 22 may line the top wall I3. Banks of tubes 23 are provided for connecting the rear header I8 with the upper front header I6, and banks of tubes 24 may also be provided between the rear header I8 and the steam drum I5, these tubes lining portions of the inner part of the rear wall I I. A bank of tubes 25 is provided for lining the upper portion of the front wall I0 and extends from the front medial header I'! to the upper front header I6. The side walls I2 of the combustion chamber are preferably. provided with suitable tubes 26 extending from the lower side wall header 20 to the upper side Wall header 2I, and the upper side wall header 2| is preferably connected by suitable banks of tubes 2'! to the steam drum I5. The lower side wall head-' ers 20 may be connected by suitable banks of tubes 28 and 29 to the medial front header I1.

The path of the gases within the walls is prefthe following description taken in connection erably directed by means of suitable baffle o that the gases are directed in heat exchange relationship with the banks of tubes. One of these baffles as at 32 may be provided along the uppermost rows of tubes of the bank of tubes 23, and baffle members 33 may also be provided for directing the gases into contact with the bank of tubes 22 between the upper front header It and the steam drum i5.

An economizer 35 is preferably provided in the upper rear portion of the casing of the steam generator and is preferably connected to the steam drum if: by suitable banks of tubes 36.

The steam drum I preferably has steam out let pipes Bl which lead to an inlet header 38 n of a superheater, the superheater tubes 39 being disposed in the pass provided between the baffle 32 and the baffle members 33. The superheater has a superheater header 40 from which superheated steam is supplied for use as desired.

The air heater 42 is provided for preheating the air supplied to the furnace for combustion by the hot gases and is preferably disposed to the rear of the steam generator so that the hot gases "of combustion may enter the air heater 4-2 'after they leave :the economizer 35. In the air-heater 42 the hot gases entering at the gas inlet -43 pass in heat exchange relation with air entering the air heater 52 at an air inlet :34, the air being supplied to the air inlet M from a forced draft air blower (not shown) and discharged through an air outlet 45 to a supply duct 46. The hot gases from the gas outlet 41' of the air preheater 42 are drawn by an induced draft fan (not shown) for discharge.

The structure for introducing the fuel material, as illustrated in the drawings, preferably includes a storage bin 50 to which the shredded fuel-material is supplied and the storage bin 50 is disposed 'in front of the front wall it of the steam generator. This bin 59 has one or more screw conveyors 5| at the bottom thereof so that the shredded fuel material may be removed from the bin 59 for "delivery for combustion. The fuel inlet includes a substantially horizontally disposed duct "52 leading into the combustion space of the steam generator, the inlet preferably being disposed 'below the header H, and having a floor portion 53 to which the fuel material falls from the conveyor 51.

The air supply duct it is connected by a duct 47 to'the fuel inlet 'duct 52 and a suitable damper 54 is provided for controlling the flow of "air. The floor 53 permits the fuel material falling thereto to be picked up by the preheated air flowing through the duct 52 so that the shredded fu'el material is carried in suspension in the air stream into the combustion space. The ducts fl'extend from the rear to the front-of the steam generator along the side walls !2, 'the side Wall ducts 41 being connected by a duct 55 which extends along the front wall Hi.

The ductst? each have a plurality of air supply pipes 69 connected thereto. These air supply pipes 60 as shown in detail in Fig. 5, have dampers 6| therein for regulating the flow of air therethrough, have the ends s2 thereof disposed substantially horizontally, and tapered and reduced in diameter for directing the stream of air passing therefrom,as hereinafter pointed out. The terminal ends '62 of the air supply pipes 60 are preferably disposed along the side walls H2 at the lowermost part thereof and are in communication with the combustion space a short distance above the floor It.

Supplemental air supply pipes 65 as illustrated in detail in Fig. 4, are also provided, these being connected to the ducts t! and being disposed along the side walls [2 and in communication with the combustion space. The terminal ends 66 of the pipes 65 are located above those of the air supply pipes 60 and are inclined downwardly at an angle with respect to the side walls l2 and to the floor I4. Dampers 6'! are provided in each of these pipes 65 for regulating the flow of air therethrough. The terminal ends 65 are disposed between tubes of the banks of tubes 26 preferably tapered to provide reduced end portions for directing the stream of air passing therefrom, as hereinafter referred to.

The manner of operating the steam generating unit of the present invention will now be pointed out.

i The preheated air from the air heater 42 passing through the duct 46, the duct 41 and the duct 52 under the control of the damper 54, sweeps across the path of the falling fuel material withdrawn from the bin '50 by the conveyor '51. As the fuel material falls toward the floor-53 in the duct 52 it is picked up and car-- ried by the stream of preheated air into the combustion space in suspension in the air. Upon their entry with the air into the combustion space the particles of'the fuel material, by reason of their weight, tend to fall toward the floor M of the furnace chamber. The unburned and unconsumed portions-of the fuel material collect in a pile upon the floor 1-4. 'The burning gases passing upwardly from the pile across the path of the fuel material which-is moving downwardly.

The water which is present in the fuel material is rapidly driven 'ofi during the descent of the fuel material and combustion "of the :pieces of the fuel material is initiated. The fuel material upon reaching the floor M is in a dry and partly burned condition and in a burning state.

The air from the lower nozzles '62, under the control of the dampers fi'Lis'directed against the pile of the material on the floor Hi 'and at the lower portion thereof at a plurality of locations along the pile between the front wall 10 and the rear wall -I l. Thestre'ams 'of air from the nozzles 62 create a condition of turbulence at the surface of the pile and small pieces of combustible material are blown from the pile and are burned adjacent the pile in suspension in the air. At the same time other and heavier pieces which remain on the pile are also burned by the air supplied thereto to create the condition of turbulence.

The air entering the combustion space through the supplemental air supply pipes 65 also strikes the pile of dry and burning material at a plurality of locations between the front wall I!) and the rear wall ti, and at a higher elevation than the air delivered 'bythe nozzles '62. The streams of air from the nozzles 66 set up -a mumm of turbulent masses at and near the pile and these masses and streams cross and intermingle in part with the turbulent masses which are brought about by the-action of the air from the lower air nozzles '52. The air from the nozzles 66 blows from the pile small pieces o'f-combustible material which are burned adjacent the pile in suspension in the air, and at the same time other and heavier pieces remaining'on the pileand in the path of the air fromthe nozzles'fifiare burned by the air supplied thereto.

It has been found in practice that a velocity of the air entering the combustion spacethrough the nozzles 62 and 69, of the order of 5000 to 6000 feet per minute is satisfactory.

The direction of the air streams from the upper air nozzles 65 and the control of the quantity of air entering at the upper air nozzles 66 is such that turbulence is increased beyond that set up by the air entering through the lower air nozzles 62. The quantity and velocity of the air as well as the location of the nozzles 62 and B6 is such that the fuel material and burning solid material are not carried upwardly in the rising stream of gases in the combustion space and the carry over from the combustion space of solid unconsumed material is reduced to a minimum.

The air entering the combustion space through the air inlet 52 aids in the completion of the combustion of the hot gases and burning materials rising above the upper air nozzles 66 so that the combustible material is completely burned in the combustion space.

The air introduced through the air inlet 52 in practice is of the order of 20% of the total of air supplied for combustion.

The tubes 25 lining the front wall [0, the tubes 26 lining the side walls I2, and the tubes of the banks of tubes 23 and 24 are utilized for steam generation by the radiant heat of the combustion.

The hot gases of combustion also pass across the tubes of the bank of tubes 23 and around the end of the bafile 32 and then successively across the superheater tubes 39, the banks of tubes 22, and then along the tubes of the banks of tubes 22, the flow being directed by the bafile members 33. The hot gases then pass into the economizer 35 and from the economizer 35 through the air heater 42 from which they are withdrawn.

Provision is also made with the steam generator of the present invention for operation, if desired, with oil burners mounted in the front wall I of the steam generator, the oil pipes being indicated at and air being supplied thereto from the wind box H which is connected to the duct 55. A damper 12 is provided for shutting off the air to the wind box II when the oil burners are not in use.

I claim:

1. Apparatus for burning woody waste material for steam generation including a furnace chamber having vertical side walls and a continuous dry imperforate floor, feeding devices for supplying preheated air and woody waste material entrained therein to said chamber, said feeding devices being located in the side walls and spaced above the floor, whereby solid unconsumed portions of said woody waste material may fall onto said floor in a pile with outer surfaces inclined inwardly from the walls of the furnace chamber, and means for supplying preheated air at high velocity for direct impingement on the inclined surfaces of the pile of unconsumed solid woody waste material, said means including nozzles below the feeding devices and above the floor at spaced locations in opposed vertical side walls of the furnace chamber.

2. Apparatus for burning woody waste material for steam generation including a furnace chamber having vertical side walls and a continuous dry imperforate floor, feeding devices for supplying preheated air and woody waste material entrained therein to said chamber, said feeding devices being located in the side walls and spaced above the floor, whereby solid unconsumed portions of said woody waste material may fall onto said floor in a pile with outer surfaces inclined inwardly from the walls of the furnace chamber, and means for supplying preheated air at high velocity for direct impingement on the inclined surfaces of the pile of unconsumed solid woody waste material, said means including nozzles below the feeding devices and above the floor at spaced locations in opposed vertical side walls of the furnace chamber and spaced downwardly inclined nozzles below the feeding devices and above the floor at a different level from said other nozzles, whereby the solid woody waste on the inclined surfaces of the pile is burned at a plurality of spaced locations thereon.

JOSIAH H. ROI-IRER. 

